A conventional orthogonal frequency division multiplexing signal receiving apparatus is constituted to generate a received signal per sub-carrier by performing a discrete Fourier transform capable of transforming discrete data, the number of which is greater than or equal to that of a sub-carrier, after transforming a frequency of a received signal into a predetermined frequency band and performing a serial-parallel transform (see Non-Patent Document 1). When QPSk (Quadrature Phase Shift Keying) or QAM (Quadrature Amplitude Modulation) is employed as a sub-carrier modulation scheme, demodulation of each sub-carrier is implemented by correcting amplitude and a phase of a sub-carrier (hereinafter, also referred to as “equalization”) based on a result of estimating an amplitude variation amount and a phase variation amount of each sub-carrier in a channel (hereinafter, also referred to as a “channel estimation”) using, for example, a known signal (hereinafter, also referred to as a “pilot signal”) previously inserted in a transmitted signal.
Patent Document 1: Japanese Patent Application Laid-Open No. 2000-236313 (FIG. 9)
Non-Patent Document 1: Itami Makoto, “Comprehensible OFDM Technique,” Ohmsha, pp. 39-44.
The conventional receiving apparatus performs the discrete Fourier transform represented by a FFT (Fast Fourier Transform) in accordance with a symbol synchronization timing between transmission and reception with respect to a received signal which frequency is transformed to a predetermined frequency, to calculate a received signal per sub-carrier. Accordingly, in the cases when a sub-carrier frequency is not synchronized between transmission and reception, when inter-symbol interference among symbols is caused by symbol timing synchronization errors, and when a Doppler shift of a sub-carrier frequency is caused by a time variation of a channel characteristic, the problem arises that inter-carrier interference gets larger, increasing the probability of erroneously regenerating a transmitted signal.